Fractographic analysis of failed porous and surface-coated cobalt-chromium alloy total joint replacements

Fractographic analyses were performed on retrieved porous and surface-coated cobalt-chromium alloy prostheses which were revised because of metallurgical fracture. Two femoral neck fractures and one fractured post of a femoral component of a total knee replacements were retrieved and analyzed via light, stereo and scanning electron microscopy (SEM). In all cases, fatigue was the mechanism of failure. The life time of these prostheses was 3-5 years. The porous coating; microstructural features, including large grains, carbides, porosity, inclusions and defects; design and manufacturing defects were all likely causative factors in these fatigue failures. In light of these and other reported fractures, further study of fatigue mechanisms and improvement of design and manufacturing processes are warranted.